EP1307302B1 - Roll stand comprising a crown-variable-control (cvc) roll pair - Google Patents

Abstract

The invention relates to a roll stand comprising a crown-variable-control (CVC) roll pair, preferably a CVC working roll pair and a back-up roll pair, which comprise a contact area (B cont) in which a horizontally active torque (M) acts that leads to a twisting of the rolls and thus to axial forces in the roll bearings. In order to keep the axial forces in the roll bearings as small as possible, the torque (M) is minimized by an appropriate CVC grinding.

Description

The invention relates to a roll stand with a CVC roller pair, preferably a CVC work roll pair and a backup roll pair having a contact area in which acts a horizontally acting moment that leads to a Entanglement of the rollers and thereby to axial forces in the roller bearings leads.

EP 0 049 798 B1 describes a rolling mill with work rolls, optionally supported on back-up rolls or back-up rolls and intermediate rolls, wherein the work rolls and / or backup rolls and / or intermediate rolls against each other axially displaceable and each roller at least one of these Roller pairs with a curved towards running towards a bale end Contour is provided, which is followed by the two rollers respectively extends opposite sides over part of the Walzgutbreite. in this connection the rolled strip cross section is almost exclusively due to the axial displacement the rollers provided with the curved contour, so that the use of a roll bending is unnecessary. The curved contour of both Rolls runs over their entire bale length and has a shape that is complemented in a certain axial position of both rolls complementary.

From EP 0 294 544 B1 roll forms are known whose contour by a Polynomial fifth order is described. This roll form still allows further corrections of the rolled strip.

To minimize bearing forces and skew rolling forces considerably in JP-A-61-296904, the contours of the work rolls with a to provide such curvature that they are parallel to the roll axis Line cuts three times. The curved contours extend doing so on both rollers in each case so opposite sides that the formed from two rolls total diameter over the entire length of the roll stays the same.

However, in the aforementioned documents, it is not considered that during the rolling process with CVC rollers, not only the rolled chip shape and profile setting range play a role. In particular, the construction cost of the roller bearings is by Axial forces of the rolls affected by the use of an inappropriate cut shape can arise.

Due to the - albeit small - diameter difference over the Bale length of a CVC roller result in different contact forces and Peripheral speeds.

In the places of the paired rolls, which have the same diameter, their peripheral speeds are the same. At the other locations of the roller contact area are the diameter and thus the peripheral speed a roller each smaller or larger than their paired roller. from that Depending on the definition of the coordinate direction, a negative or positive result Speed difference between the paired rollers over their Contact area.

The different sized and differently oriented relative speeds lead to differently sized and differently directed circumferential forces. This distribution of roller peripheral forces causes a moment around the center of the scaffolding, which is used to secure the rollers and thus to axial forces can lead in the roller bearings.

From JP-A-6-285518 it is known the contour of axially displaceable against each other To form work rolls according to a higher-order polynomial, where the highest term is the distance from the roll center in the direction of the roll axes and three more terms concerning the point symmetry. The contours The work rolls are designed so that the integration of the product from the roll radius and the distance from the roll center in the direction of Roller axles over the entire contact length with another roller, for example a backup roll, the value zero. By such a contour the work rolls can occur bearing forces u. a. through the Inclination of the work rolls are generated, humiliated.

The invention is based on the object, in a generic rolling mill Provide measures that minimize the axial forces of the roller bearings become. The task is characterized by the characterizing features of Claim 1 solved. Simply by changing the shape of the CVC rollers The moments acting in a horizontal direction can be done without additional effort be minimized.

L = Radius der CVC-Walze

a_i = Polynomkoeffizienten

x = Koordinate in Ballen-Längsrichtung

A suitable change of the shaping is inventively achieved in that the radius profile of the CVC roller by the Polynomansatz R (x) = a 0 + a 1 • x + a 2 • x 2 + ...... + a n • x n described and preferably the so-called wedge factor a _{1 is used} as an optimization parameter. The contour of a CVC roller is defined by a third-order polynomial: R (x) = a 0 + a 1 x + a 2 x 2 + a 3 x 3 With

L = radius of the CVC roller

a _i = polynomial coefficients

x = coordinate in bale longitudinal direction

For higher-order CVC rolls, additional polynomial terms (a ₄ , a ₅ , etc.) are taken into account.

The polynomial coefficient a ₀ results from the current roll radius. The polynomial coefficients a ₂ , a ₃ and a ₄ a ₅ , etc. are set so as to give the desired setting range for the CVC system. The polynomial coefficient a ₁ is independent of the adjustment range and line load between the rollers and thus freely selectable. This wedge factor or linear component a ₁ can be selected so that minimal axial forces occur when using CVC rollers.

For reasons of practicability, the optimum wedge factor a _{1 is determined} offline and as an average value from various shift positions of the CVC rollers (eg minimum, neutral and maximum shift position). Although a complete compensation of the axial forces of the roller bearings is not achieved by averaging, but a minimum value of the same over the entire adjustment range of the rollers.

With optimized wedging of the CVC-cut, the tangents, the one Final diameter at the concave side of the roller and the convex portion of the roller Touch the roller and the tangent to the other end diameter (at the convex side of the roller) and the concave portion of the roller touch each other parallel and opposite the roll axes around the optimum wedge angle inclined. For conventionally ground CVC work rolls that are aimed at smallest diameter differences were designed, these tangents run but also parallel to the roll axis.

Due to mathematical considerations and empirical data, it has proved to be advantageous that the wedge factor a ₁ for a roll with a 3rd order polynomial set in the range of a 1 = - 1 20 to - 5 20 • a 3 B 2 cont lies.

Corresponding considerations lead to the wedge factor a ₁ for a roller with a 5th order polynomial expression through the expression a 1 = f 1 • a 3 B 2 cont + f 2 • a 5 B 4 cont is describable, with f 1 = - 1 20 to - 5 20 and f 2 = 0 to - 7 112

Further features of the invention will become apparent from the claims and the following description and the drawing, in the embodiments of the invention are shown schematically.

Fig. 1a, 1b und 1c

ein CVC-Arbeitswalzenpaar in unterschiedlicher Verschiebeposition und mit Stützwalzen sowie die Linienlastverteilung im Walzspalt und zwischen den Walzen,

Fig. 2

Umfangskraftverteilung im Kontaktbereich zweier Walzen,

Fig. 3

CVC-Arbeitswalzenpaar mit konventionellem Schliff,

Fig. 4

CVC-Arbeitswalzenpaar mit optimaler Keiligkeit.

Show it:

Fig. 1a, 1b and 1c

a CVC pair of work rolls in different displacement position and with back-up rolls as well as the line load distribution in the roll gap and between the rolls,

Fig. 2

Circumferential force distribution in the contact area of two rolls,

Fig. 3

CVC work roll pair with conventional grinding,

Fig. 4

CVC pair of work rolls with optimum wedging.

In FIGS. 1a, 1b and 1c, CVC work rolls 1 are in different Displacement positions shown. The work rolls 1 are of support rollers. 2 supported. Between the work rolls 1 is a rolled strip. 3

The load in the nip is assumed to be constant over the rolled strip 3 and independent of the shift position of the work rolls 1. It is represented by arrows 4. The load between the CVC work rolls 1 and the backup rolls 2 is distributed unequally over their contact area b _cont and changes with the shift position of the work rolls 1. This load is represented by arrows 5. The sum of the loads represented by the arrows 4 and 5 is equal and opposite.

The resulting from the roll forms load arrows 5 and the local positive or negative relative speed lead according to Figure 2 to different circumferential forces Q _i over the contact width b _cont . This distribution of the roller peripheral force Q _i causes a moment M about the roller frame center 6, which can lead to the cupping of the rollers 1, 2 and thus to axial forces in their bearings.

This is prevented by a corresponding roll grinding form. For CVC rollers with the roll contour according to a third-order polynomial theorem according to R (x) = a 0 + a 1 • x + a 2 • x 2 + a 3 • x 3 is only the factor a ₁ , the so-called wedge factor for a variation of the grinding pattern available because the polynomial coefficient a ₀ the respective roller radius and the polynomial coefficients a ₂ , a ₃ , a ₄ , a ₅ , etc. determine the desired setting range of the CVC system , Only the wedge factor a ₁ is independent of adjustment range and line load between the rollers and thus freely selectable. For CVC rollers whose contour is defined by a third-order polynomial, the wedge factor a ₁ results in a minimum moment M when in the range a 1 = - 1 20 to - 5 20 • a 3 B 2 cont lies.

For CVC rolls whose contour is defined by a 5th order polynomial, the moment M reaches a minimum when the wedge factor a 1 = f 1 • a 3 B 2 cont + f 2 • a 5 B 4 cont is with f 1 = - 1 20 to - 5 20 and f 2 = 0 to - 7 112

FIG. 3 shows a conventionally ground CVC work roll pair, which was designed with the goal of smallest diameter differences. The an end diameter 7 and the convex portion of the roller contacting tangent 8 and the other end diameter 9 and the concave portion of the Roller touching other tangents 10 are parallel to the axes of the conventionally ground work rolls. In contrast, the corresponding run Tangents of the CVC rollers according to Figure 4, with optimized Wedge were designed in parallel, but with respect to the roll axes around the optimum wedge angle • (alpha) inclined.

LIST OF REFERENCE NUMBERS

1, 1 '

CVC working rolls

2

backup rolls

3

rolled strip

4

Arrow (load in the nip)

5

Arrow (load between work roll 1 and support roll 2)

6

Mill center

7, 7 '

final diameter

8, 8 '

tangent

9, 9 '

other final diameter

10, 10 '

other tangent

Claims (2)

1. Roll stand with a CVC roll pair, preferably a CVC working roll pair (1, 1') and a backing roll pair (2), which have a contact region (b_cont) in which a horizontally acting moment (M), which leads to crossing of the rolls (1, 2) and thereby to axial forces in the roll bearings, acts, characterised in that the moment (M) is minimised by an appropriate CVC grinding of the rolls (1, 1') with a radial course (contour) of the CVC rolls (1, 1') defined by the polynomial equation: R(x) = a0 + a1 • x + a2 • x2+ ... + an • xn, wherein

   R(x) =

   radial course

   x =

   co-ordinates in longitudinal direction of circumferential surface

   a₀ =

   actual roll radius

   a₁ =

   optimisation parameter (wedge factor) which is formed off-line as a mean value of different displacement positions of the CVC rolls (for example minimum, neutral and maximum displacement positions) and

   a₂ to a_n =

   setting range of the CVC system,

   wherein the CVC grinding for optimised amount of wedge is so formed that the tangents (8'), one end diameter (7') and the convex part of the roll (1') and the tangents contacting the other end diameter (9') and the convex part of the roll (1') extend parallel to one another and at an inclination relative to the roll axes by the optimum wedge angle (α).
2. Roll stand according to claim 1, characterised in that the optimisation angle a₁ for a roll (1, 1') with a radial course according to a polynomial equation of 3rd order lies in the region of a1 = f1 • a3 • b2 cont and for a roll (1, 1') with a radial course according to a polynomial equation of 5th order lies in the region of a1 = f1 • a3 • b2 cont + f2 • a5 • b4 cont, wherein f₁ = 1/20 to 5/20 and f₂ = 0 to 7/112.

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